The present invention relates to an apparatus and a method for controlling a distance between two traveling vehicles and a recording medium for storing the control method.
To improve the safety in a vehicle driving operation and reduce the driver's burden, an apparatus for automatically controlling a distance between two traveling vehicles is conventionally proposed. For example, a relative speed between the system's vehicle and a preceding vehicle is obtained. A target distance is determined in accordance with the detected relative speed (i.e., speed deviation between two vehicles). An actual distance between the system's vehicle and the preceding vehicle is detected. To eliminate the distance deviation between the actual distance and the target distance, an appropriate target acceleration is set to control an internal combustion engine of the vehicle and/or a braking apparatus so as to realize the target acceleration.
The target distance is fixed to a predetermined value when the vehicle speed is constant. The target distance is changeable in accordance with the change of the vehicle speed. The target acceleration is thus calculated based on the distance deviation between the actual distance and the target distance corresponding to the present vehicle speed.
In other words, when the distance deviation is a same value, a same target acceleration is obtained regardless of the difference in the target distance set by the driver. This makes drivers uncomfortable.
For example, the driver may set a relatively long target distance in a first driving condition and a relatively short target distance in a second driving condition. It is assumed that the distance deviation is same for both cases. In this case, unless there are any other different conditions, the same target acceleration will be obtained for both cases.
However, it depends on the target distance whether the driver preferably accepts the obtained target acceleration or not. More preferably, the driver may think that the obtained target acceleration is preferable when he or she selects the relatively long target distance. However, this driver possibly feels that the same target acceleration is inappropriate when he or she selects the relatively short target distance. On the other hand, other drivers may think that the obtained target acceleration is inappropriate for the relatively long target distance and rather preferable for the relatively short target distance.
When the target acceleration is appropriate for maintaining the long target distance, the same target acceleration will be too moderate or dull for the system's vehicle to approach to or depart from the preceding vehicle to maintain the short target distance. On the contrary, when the target acceleration is appropriate for maintaining the short target distance, the same target acceleration will be too abrupt or steep for the system's vehicle to approach to or depart from the preceding vehicle to maintain the long target distance.
It is believed that such problems come from the improperness of the conventional distance control method because the absolute value of the distance deviation is solely used to control the target acceleration of the system's vehicle.